A multistage malaria vaccine showed encouraging levels of protection against controlled human malaria infection (CHMI) in Malian adults with lifelong exposure to the causative parasite, according to a new phase 2 randomized controlled trial published in The Lancet Infectious Diseases.

The investigational vaccine, ProC6C-AlOH/Matrix-M, targets multiple stages in the life cycle of Plasmodium falciparum, a protozoan that causes the most severe form of malaria in people. Researchers tested the vaccine in healthy adults aged 18 to 50 years in an area of Mali where malaria exposure is common.

Vaccine offers ‘novel, strong’ correlate of protection 

The researchers, from Mali, Europe, and US malaria vaccine maker Sanaria, randomly assigned the 34 participants to receive either three doses of the malaria vaccine (17 volunteers) or three doses of rabies vaccine as controls (17). The doses were administered four weeks apart. Ninety-four days after the final dose, participants were deliberately exposed to malaria through injection of a small amount of the malaria parasite under the skin.

Of the 32 participants who completed the challenge, 59% developed parasites in the bloodstream (parasitemia) within 28 days. Infection occurred in 13 of 16 control recipients, compared with six of 16 vaccine recipients (54% efficacy, although the confidence interval [CI] was wide, indicating some uncertainty). In those who became infected, vaccination delayed the median time to detectable parasitemia by 2 days (76% efficacy, also with a wide CI). 

Adverse events were more common in the vaccine group, but almost all were mild.

The study authors note that this is the first anti–P falciparum subunit vaccine to surpass 50% efficacy against CHMI at 12 weeks after vaccination, which suggests “a novel, strong, and mechanistically plausible correlate of protection.”

The researchers say future studies should assess the vaccine’s efficacy against naturally acquired malaria and in young children. In a related commentary, Gemma Moncunill, PhD, and Carlota Dobano, PhD, both of ISGlobal in Spain, wrote, “Having a first multistage malaria vaccine with proven efficacy is a key achievement, as there is consensus in the malaria community on the need to cover as many parasite stages as possible.”

For the first time, a deer in Wayne County, Tennessee, has tested positive for chronic wasting disease (CWD), authorities announced yesterday.

The detection was in a road-killed deer, the Tennessee Wildlife Resources Agency (TWRA) said in a news release. Wildlife-feeding and carcass-transportation restrictions are in place, because Wayne County was already included in the state’s CWD management zone. 

Located in south-central Tennessee, Wayne County borders Alabama and Decatur County, Tennessee, which reported its first CWD case earlier this month. 

While deer hunting season dates and regulations won’t change as a result of the case, Wayne County hunters are now eligible for the Earn-a-Buck Program, which allows them to harvest additional bucks by harvesting antlerless deer and submitting them for CWD testing.

“Hunter’s participation in CWD testing is critical for the continued surveillance and monitoring of CWD throughout the state,” TWRA said. “Hunters can access CWD testing through participating taxidermists and meat processors or by using drop-off freezers.” 

Disease found in 36 US states, 5 other countries

CWD, which affects cervids such as deer, elk, and moose, is a fatal neurodegenerative disease caused by infectious misfolded proteins called prions, which spread from direct contact and through environmental contamination. While CWD hasn’t been identified in people, health officials urge not consuming the meat of sick or infected cervids and using caution when handling carcasses.

Hunter’s participation in CWD testing is critical for the continued surveillance and monitoring of CWD throughout the state.

Since the disease was first identified in Colorado in 1967, it has spread to 35 other US states, five Canadian provinces, Finland, Norway, South Korea, and Sweden. No vaccine or treatment is available.